Heat control circuit



1952 QB. STADUM ETAL 2,623,168

HEAT CONTROL CIRCUIT Filed March 17, 1950 2 SHEETS-SHEET l Flg.lo. f;

Sequence 69 Control 67 7| FLI'LI' WITNESSES: INVENTORS Edward C.HurtwigClorenceB.Stqdum 54% oficyilliamELorge.

Dec. 23, 1952 c. B. STADUM ETAL 2,623,168

HEAT CONTROL CIRCUIT Filed March 17. 1950 2 SHEETS-SHEET 2 Fi l b.

Heot Control Squeeze WITNESSES: Z9 INVENTORS W Edword QHurtwigClorenceBStodum and Vgiyium E. Large.

ATTORNEY Patented Dec. 23, 1952 UNITED STATES PATENT emcs H w and W liam a e;Lt'l ee lN iia P nnsywanra o'r'sto- Westinghouse ElectricQorperzy- Efi t Pitt'sbfirgh; 1%., i i corporation of trodes elre r relThis event current" is interfiint'jd, the wsdirrgneceeaes are maintainedin engegefiientfw itlf'the material din ing'a SO-CaLIIe'd- Hcildlnt a1tintil th'e weldheird ens; The electrodes their diserigdged item Thematerial and me I'fed i'fri" disengagement" during a; so-cllled"Qfiiiitivfliso that thelfia tie rial maybe r'esetfor' a; second opera-em;If the" welder is set forReijeait'epereitior-r end'tliestert' switch ismaintained closed} the" alegive desc'i ihest sequence or'events isrepetede; xi'umb 'ero'f times ends, series of vsieldserecluced If thewelding is" set" for? Non-Rene 0' switch" must be r ppenee" completionof each Held interval A heat cont-rm ircuitisj sa Tb control the flow ofcurrent" durin -3 thWe1dfinteT 'a1 An" example of a heat contr cireiiitis" shown in Dawson. In" this 'circ'iiitj th has impressed betwe'enitsano direct current voltage.

a source-of direetflcurr the use hthe Valve ea seriously limited the u.efiime-ss b'f t'riem'wsen netion with such a; timer sinee Demon-relies;1

'intervst of prope 1011; the start ecloseii after the w en Te It isanother obje'et of our invention to'p ev -eiea; heat controleireiiit'i'nf which the flow of current can be"controlledtkitllemejmerw. v

It is another obje'et of our invel'lfiiOIl fiQprU- vide' a heat controleirc'xiit having a minimumo'f circuit components. 1 v i In accordancewith our intention; we protigle a, heat eontrol time haVing eieapadltorconnected between its control electrode and its cathode. The capeeitor'is charged atthe'beginning of the Weldinter'vel through: aghelf avereeti fi rr he heat 'ejontrol tuh is eonnected toa control transformerthrough e; plurality of resistors. These resistors normally 1mm the newor current to such extent that the ignitrbns" of the powei circiiit do'not become Oi diietiv'et Two vellves are'connecteclto" shunt theseresistors. A anable phase shift" circuit controls the; conductivityof'the'se two shunt valves. A ya'riablD. C. bi'egs,

oonnectedbetween the cathd'desend grids of the two shunt vaflvs';fnrthericontrels"their conductiv ity; Such a!heetcontrdlcireuit'hasanumber of variable control elements" and: ce'iibe" use'djwith theconventional half Wave rectifier sequence T e Revel i 't rsiwh l h en'sm r Ch a? teristic of our inventionere set] forth Withpa-r ticularityin the jeppended c aims; The invention 1 itself, however, both as to itsorganization and methddoff pperetion together with"atlditionel' objectsand ajdvanteg'es thereof will best be gnderstbbd from; the following cl'es eriptien qf"a specifir; embodiment? wh n; Tee'cl in connection Withthe atteche'd drawings; Figs; 1a end; 1b, whieh form two parts of acircuit diegreni sh o wing' a prferred'e'rnbo-dl'ment ofto m i tioh'. vv

separate shownin thedralw in gs 00in prises a welding" transformer '5 acrdss the seconeletry of which weldingeletroiies 1 and 9 "are connected.One"=e'f these eleetrogles Tmay b'ej move din-t0 and but 'Of eflgagemfitwith the Work llrbyopemtion'bf a'hydrauli' system I31 Power "is suppliedto the" primary of the transformer Eifrom busesl5',--whi'ch'ma,y"be theeases of a.

commercial supply of 200t0'2300'noh'1inalvo1tege rating; through 'apairof-ignitro'ns'l'l and" I9 connected inantiparallebbetweenth buses and"the primary; Firing-= thy-ratrons 2 I and" 23 respeetiyely are providedior the ignitrons'il l and 19; These thyratrens becomeeondu'ctive in response to-impnlses from the secondarie's' 20" and Y, t fi e firensf rmer2 To r v r. r.

The operation of the welding electrodes 1 and 9 and the supply ofwelding current is controlled from a sequence timer devoid of sequencingelectrcmagnetic relays. This timer determines the duration and the orderof occurrence of the Squeeze, Weld, Hold and Off intervals. It includesinitiating thyratrons 35, 31, 39 and ii respectively. The Squeezethyratron 29 and two of the start thyratrons 26 and are necessarily ofthe type having an anode 43; a cathode 45 and a plurality of controlelectrodes 41 and 49; and others may be of the same type but may be asshown of the type having an anode 65, a cathode 9'! and only one controlelectrode 99. While the valves 29, 3|, 35, 31, 39 and M are thyratronsin the preferred practice of our invention, certain or all of the valvesmay, under some circumstances, be high vacuum electric dischargedevices, ignitrons or discharge devices of other types.

Between the control electrodes 69 and the oathodes 61 of the Weldthyratron 3| and the Hold thyratron 63 are connected the Weld and Holdtime constants networks II and 19, respectively. Between the controlelectrodes and oath-odes of the Squeeze, Hold and Start thyratrons 29,33, 25 and 2B is a potentiometer and a transformer secondary. Thevoltage in the primary of these transformers is phase shifted so thatthe voltage peak through the secondary comes early in the positive halfcycle between the anode and cathode of the Squeeze, Hold and Startthyratrons. The thyratron 29 is connected to the control grid I2 of theheat control thyratron I3 to bias it to conductivity during the weldinterval. Two auxiliary heat control thyratrons I4 and TI are connectedin series with the heat control thyratron I3. A variable D. C. bias I9is connected between the cathode BI and the control grids 83 of theauxiliary thyratrons I4 and I1. A transformer variable phase shifter 85provides a firing voltage. The heat control circuit is coupled through atransformer 24 to the thyratrons 2| and 23 which fire the weldingignitrons I1 and I9.

The valves of the sequence timer have cathodes heated by power from theheating transformer 2. The heating transformer 'has two secondaries 3and 4. The first secondary 4 is connected directly to the heaterelements, while the second secondary 3 is connected through a resistor 6to other heater elements.

The first secondary 4 provides heating current for the thyratrons 31,39, 35, 2B and 33 which are initially conductive. The second secondary 3is connected to the thyratrons 26, 25, 3I, 4|, and 29 which must not beinitially conductive.

The windings of the transformer 2 are such that the first secondary 4impresses rated voltage on the heater connections. The second secondary3 impresses rated voltage on the heater only when rated current isflowing. When the heater circuit is first closed, all the heaters takemore than rated current. The first secondary 4 still impresses ratedvoltage onthe heater, but a portion of the voltage impressed by thesecond secondary 3 appears across the resistor 6. The heatters of thethyratrons connected to the second secondary 3, then, are subject toless than rated voltage. The thyratrons on which rated voltage isimpressed will heat up faster than those connected to the secondsecondary 3 and become conductive first. By means of this circuitarrangement, the thyratrons which are required to be initiallyconductive will heat up and become conductive first. The arrangement ofthe timer circuit is such that proper operation follows if the correctthyratrons are initially conductive.

To initiate operation of the circuit, the start switch 81 is closed.Prior to closure of the start switch 81, an auxiliary thyratron 28 isconducting current to charge the bias capacitor 89 through a resistor91. The charge on the capacitor '89 normally maintains the start tubes25 and 29 non-conductive. Closure of the start switch 81 connects thegrids 49 of tubes 25 and 26 to their cathodes 45, thus initiatingconduction through them. Current conducted through the first start tube29 actuates the solenoid 93 of the hydraulic mechanism I3 to close thewelding electrodes on the work piece. Current conducted by the secondstart tube 25 charges the capacitor 95 of the time constant circuit 91associated with the auxiliary tube 28. The capacitor 95, when charged,causes the potential of the grid 69 of the auxiliary thyratron-28 tobecome negative with respectto the cathode B1 and the auxiliarythyratron 28 become non-conductive.

The value of the resistors 99, NH, I93, I95 is so chosen that thepotential impressed across the timing capacitor 89 when the auxiliarytube is conductive is approximately 28 volts R. M. S. A transformer isused to supply volts for control. Thus the start switch 81 closes acircuit across which is impressed approximately 28 volts instead of theusual 115 volts impressed across the start switch in conventionalcircuits.

The secondary auxiliary thyratron 35 becomes conductive when the firstauxiliary thyratron 29 becomes conductive. Prior to initiation ofoperation of the sequence timer, the second auxiliary thyratron 35 hasbeen conductive, charging through a resistor I91 the timing capacitorI99 ofthe Squeeze time constant circuit II I. When the second auxiliarythyratron 35 becomes nonconductive, the Squeeze time capacitor I99discharges through the resistor H3 and the potentiometer H5. Thepotentiometer H5 can be varied to vary the time constant of this networkIII and, accordingly, the Squeeze time.

After a period of. time determined by the setting of the potentiometerH5, the bias presented by the time contact network III is sufiicientlylow that the voltage across a portion of potentiometer III causes theauxiliary thyratron 4| to become conductive early in the positive halfcycle of voltage between its anode 55 and cathode 61. The control gridof the squeeze thyratron 29 is connected to the same timing circuit III.The thyratron 29, therefore, becomes conductive when the thyratron 4!becomes conductive. The thyratron 29, when conductive, charges thecapacitor I I9 in the grid circuit of the heat control thyratron 13. Thevoltage across capacitor H9 is added to the voltage across the biasingcapacitor I2I to cause the heat control tube 13 to become conductive.The resistor I23 in parallel with capacitor H9 is of such value that thecapacitor H9 retains its charge long enough to cause the tube I3 toconduct two pulses of current during every cycle of the control voltage.

Impressed across the heat control thyratron I3 is the voltage betweenthe midtap I25 and one end of the secondary I2'I of the transformer I29.During one half cycle of the supply the heat control thyratron I3conducts electron current through the resistor I3I, a portion of thesecondary I21, the primary I33 of the firing transformer 24, the currentlimiting resistor I35 to the heat control thyratron 73. The currentflowing through transformer primary I33 is insufiicient former, andmeans for shunting said resistance means at a predetermined time.

2. In combination, an electric discharge valve having an anode, acathode and a control electrode, a transformer having a primary and asecondary, said transformer secondary being connected between thecontrol electrode and the cathode of the electric discharge valve,resistance means, a second electric valve, a source of voltage, seriesconnections between said second electric discharge valve, saidresistance means, said source of voltage, said primary of thetransformer and electric valve means shunting said resistance means, acontrol electrode in said electric valve means and a variable phaseshift circuit connecting said control electrode to said source ofvoltage in such a way that the voltage of said source controls theconductivity of said electric valve means.

3. In combination, an electric discharge valve having an anode, acathode and a control electrode, a transformer having a primary and asecondary, said transformer secondary being connected between thecontrol electrode and the cathode of the electric discharge valve,resistance means, a second electric valve, a source of voltage, seriesconnections between said second electric discharge valve, saidresistance means. said source of voltage, said primary of thetransformer and electric valve means shunting said resistance means, ananode, a cathode and a control electrode in said electric valve means, aphase shift circuit connecting said control electrode to said source ofvoltage, and a variable source of direct current connected between thecathode and anode of said electric valve means, to form a variable biastherefor.

l. In combination, supply terminals; load terminals; a timer; acapacitor; connections between said supply terminals, said timer andsaid capacitor for supplying current to said capacitor duringpredetermined discrete time intervals determined by said timer; first,second and third electric discharge valves, each having an anode, acathode, and a control electrode; connections between said capacitor andsaid control electrode and said cathode of said first valve; connectionsbetween said first and said second valves and said supply terminals toconduct current of one polarity from said supply terminals through saidload terminals; connections between said first and said third valves andsaid supply terminals to conduct current of the other polarity from saidsupply terminals through said load terminals, and means for impressing acontrol voltage on the control electrodes of said second and thirdelectric discharge valves.

5. In combination, supply terminals; load terminals, a timer; acapacitor; connections between said supply terminals, said timer andsaid capacitor for supplying current to said capacitor duringpredetermined discrete time intervals determined by said timer; first,second and third electric discharge valves, each having an anode, acathode, and a control electrode; connections between said capacitor andsaid control electrode and said cathode of said first valve; connectionsbetween said first and said second valve and said supply terminals toconduct current of one polarity from said supply terminals through saidload terminals; connections between said first and said third electricvalves to conduct current of the other polarity from said supplyterminals through said load, and a resistor connected in parallel withsaid second valve.

6. In combination, supply terminals; load terminals; a timer; acapacitor; connections between said supply terminals, said timer andsaid capacitor for supplying current to said capacitor duringpredetermined discrete time intervals determined by said timer; first,second and third electric discharge valves, each having an anode, acathode, and a control electrode; connections between said capacitor andsaid control electrode and said cathode ofsaid first valve; connectionsbetween said first and said second electric discharge valve and saidsupply terminals to conduct current of one polarity from said supplyterminals through said load terminals; connections between said firstand saidthird valves; and means for impressing on the control electrodesof said second and third valves a control voltage of a predeterminedphase different from the phase of the voltage of said supply terminals.

7. In combination, supply terminals; load terminals; a timer; acapacitor; connections between said supply terminals, said timer, andsaid capacitor for supplying current to said capacitor duringpredetermined discrete time intervals determined by said timer; first,second and third electric discharge valves, each having an anode, acathode, and a control electrode; connections between said capacitor andsaid control electrode and said cathode of said first valve; connectionsbetween said first and said second valve and said supply terminals toconduct current of one polarity from said supply terminals through saidload terminals; connections between said first and said third valves;means for impressing on the control electrodes of said second and thirdvalves a control voltage of a predetermined phase different from thephase of the voltage of said supply terminals; means for varying thephase of said control voltage; and means for impressing a variableunidirectional control voltage on said control electrodes of said secondand third valves, said last voltage being so impressed on said controlelectrodes that it adds algebraically to said variable phase controlvoltage.

8. In combination, supply terminals; load terminals; a timer; acapacitor; connections between said supply terminals, said timer andsaid capacitor for supplying current to said capacitor duringpredetermined discrete time intervals determined by said timer; meansforming with said capacitor a time constant circuit having a timeconstant of approximately one cycle; first, second and third electricdischarge valves, each having an anode, a cathode and a controlelectrode; connections between said capacitor and said control electrodeand said cathode of said first valve; connections between said first andsaid second valves and said supply terminals to conduct current of onepolarity from said source through said load; connections between saidfirst and said third valves and said supply terminals to conduct currentof the other polarity from said supply terminals through said loadterminals and terminals for impressing a control voltage on the controlelectrodes of said second and third valves.

9. In combination valve means for controlling the flow of current froman alternating-current source through a load, a circuit connected tosaid valve means for rendering said valve means conductive and includingmeans to determine the instants in each cycle of said source at whichsaid valve means becomes conductive, a timer for measuring apredetermined period of time, said time including an electric valvecontrolled by said timer to conduct current for said predeterminedperiod of time, a second electric valve in said circuit adapted topermit conduction in said circuit only when said second valve isconductive, and connections between said first and said second valvesuch that said first valve controls the conductivity of said secondvalve.

10. In combination valve means for controlling the flow of current froman alternating-current source through a load, a circuit connected tosaid valve means for rendering said valve means conductive and includingmeans to determine the instants in each cycle of said source at whichsaid valve means becomes conductive, a timer adapted to measure apredetermined period of time and including an electric valve controlledby said timer to conduct current for said predetermined period of time,a second electric valve having an anode, cathode and control electrodein said circuit adapted to permit conduction in said circuit only whensaid control electrode is at or above a predetermined potential withrespect to said cathode, an impedanc connected between said controlelectrode and said cathode, and a circuit between said first electricvalve and said impedance.

11. In combination valve means for controlling the flow of current froman alternating-current source through a load, a circuit connected tosaid valve means for rendering said valve means conductivev andincluding means to determine the instants in each cycle of said sourceat which said valve means becomes conductive, a timer adapted to measurea predetermined period of time and including an electric valvecontrolled by said timer to conduct current for said predeterminedperiod of time, a second electric valve having an anode, cathode andcontrol electrode in said circuit adapted to permit conduction in saidcircuit only when said control electrode is above a predeterminedpotential with respect to said cathode, energy storage impedanceconnected between said control electrode and said cathode, a circuitbetween said first electric valve and said impedance, and a circuit forsubstantially discharging said impedance in a time interval of onecycle.

12. A heat-control circuit including a power supply winding havingterminal taps and an intermediate tap; a first electric discharge devicehaving an anode, a cathode and a control electrode; a second electricdischarge device having an anode, a cathode and a control electrode; aconnection between said anode of said first device and one terminal tap;a connection between said anode of said second device and said otherterminal tap; an auxiliary discharge device having an anode and acathode; a connection between the cathodes of said first and seconddevices and said anode of said auxiliary device; output means;connections connecting said intermediate tap, said output means and saidcathode of said auxiliary device in series; means for supplyingpotential between the control electrodes and the oath-- odes of saidfirst and second devices adapted to render said devices conductive atpredetermined instants in the periods of said supply winding and aresistor connected in parallel with said anode and cathode of at leastsaid first device.

13. A heat-control circuit according to claim 12 characterized by aphase shift network having a pair of output terminals and by connectionsfrom each output terminal to a control electrode respectively of thefirst and second devices.

14. A heat-control circuit according to claim 12 characterized by atimer connected to control the conductivity of the auxiliary device.

CLARENCE B. STADUM. EDWARD C. HARTWIG. WILLIAM E. LARGE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,361,846 Garman Oct. 31, 19442,406,853 Richardson Sept. 3, 1946 2,409,522 Woll Oct. 15, 19462,415,654 Place Feb. 11, 1947 2,415,870 Ryder Feb. 18, 1947 2,421,995Cooper June 10, 1947 2,438,017 Murcek Mar. 16, 1948 2,463,318 SchneiderMar. 1, 1949 2,516,422 Rockafellow July 25, 1950

